Changing a gene’s activity can cause cancer, even though the DNA itself hasn’t mutated, a new study demonstrates.

The finding is some of the first direct evidence that epigenetic changes can cause cancer. Epigenetic modifications are chemical tags tacked onto DNA or associated proteins. Such tags alter gene activity without changing the information in genes.

Scientists have long suspected that epigenetic modifications contribute to cancer. “The problem is, all of the studies we’ve done so far h...